Fabrication of nanotube arrays on commercially pure titanium and their apatite-forming ability in a simulated body fluid

Abstract

In this study, we investigated self-organized TiO2 nanotubes that were grown using anodization of commercially pure titanium at 5V or 10V in NH4F/NaCl electrolyte. The nanotube arrays were annealed at 450°C for 3h to convert the amorphous nanotubes to anatase and then they were immersed in simulated body fluid at 37°C for 0.5, 1, and 14days. The purpose of this experiment was to evaluate the apatite-formation abilities of anodized Ti nanotubes with different tube diameters and lengths. The nanotubes that formed on the surfaces of Ti were examined using a field emission scanning electron microscope, X-ray diffraction, and X-ray photoelectron spectroscope. When the anodizing potential was increased from 5V to 10V, the pore diameter of the nanotube increased from approximately 24–30nm to 35–53nm, and the tube length increased from approximately 590nm to 730nm. In vitro testing of the heat-treated nanotube arrays indicated that Ca-P formation occurred after only 1day of immersion in simulated body fluid. This result was particularly apparent in the samples that were anodized at 10V. It was also found that the thickness of the Ca-P layer increases as the applied potential for anodized c.p. Ti increases. The average thickness of the Ca-P layer on Ti that was anodized at 5V and 10V was approximately 170nm and 190nm, respectively, after immersion in simulated body fluid for 14days.